In a recent multimedia service, a hybrid network that connects a broadcast network and a communication network at the same time and a Moving Picture Experts Group (MPEG) media transport (MMT) technology for providing hybrid contents where multimedia data, applications, and files are provided together have been considered.
FIG. 1 is a view for describing an MMT data model in a multimedia communication system.
Referring to FIG. 1, the MMT technology defines a set of encoded media data and metadata related to the media data is defined as a package 100. The package 100 may include at least one MMT assets 110, 120, and 130, at least one “asset delivery characteristics (ADC) (or “transport characteristics” information) 115 and 125, and at least one presentation information (PI) 140. The package 100 may be understood as contents such as a movie, etc.
The MMT asset means multimedia data that may be used to generate multimedia presentation such as video, audio, texts, files, etc. The respective MMT assets 110, 120, and 130 may be divided into at least one media processing unit (MPU). In FIG. 1, the MMT asset #1 110 is illustrated as being divided into a plurality of MPUs 111, 112, . . . , 113. The MPU is a unit in which an MMT stream is processed independently. The MPU is a unit of media data that may be decoded independently. One MPU may be divided into a plurality of pieces, each of which is referred to as an “MPU fragment unit”. An MMT transmission entity divides and processes media data MPU-by-MPU, and an MMT reception entity receives media data and processes the media data for reproduction MPU-by-MPU. The ADC may include information for providing a transport characteristic of an MMT asset for each MMT asset. In the example of FIG. 1, the ADC 115 indicates transport characteristics of the asset #1 110, and the ADC 125 indicates transport characteristics of the assets #2 120 and #3 130. The PI 140 may include information describing time and space relationships among the plurality of assets 110, 120, and 130, and specifies a transmission order of MMT assets in a package.
In the multimedia system to which the MMT data model is applied, a transmitting or sending entity packetizes media data formed in MPU units into multiple MMTP packets and transmits the MMTP packets. In the multimedia system, a receiving entity depacketizes received multiple MMTP packets into MPU units and reproduces reconstructed media data.
The MPU is transmitted after being packetized into multiple MMTP packets, and the MFU is transmitted through an MMTP payload of at least one MMTP packet. The MMTP packet refers to a formatted unit of media data to be transmitted using the MMTP and carries an MMTP payload. The MMTP payload means a formatted unit of media data for transmitting a package and/or signaling messages by using the MMTP or an Internet application transport layer protocol (e.g., a real time protocol (RTP)). The MMTP payload may include MPU metadata, fragment metadata, MFU, or signaling information. The MPU metadata may include information for identifying the MPU, information for decoding media data, and so forth. The signaling information may include various signaling messages for delivery and consumption of the package. Through the signaling messages, a structure of the package, a protocol configuration, a structure of the MMTP payload, and so forth may be provided to the receiving entity.
As such, in the MMT-based multimedia system, the media data is transmitted after being divided into multiple MMTP packets (that is, transmitted as a packetized media stream), and for example, the MPU metadata and the signaling information, out of information transmitted through the multiple MMTP packet, may be considered as essential information needed for the receiving entity to decode or reproduce the media data. Therefore, for reproduction of the media stream without a delay, quick reception of the MPU metadata associated with the media data and the signaling information is needed.